Sacrificial cryogen gas liquefaction system

Abstract

A liquefaction system includes a source tank containing a supply of liquid nitrogen with a head space there above filled with nitrogen vapor. A pump transfers the liquid nitrogen to a heat exchanger. The heat exchanger also receives natural gas that has been processed in a purifier. The natural gas is liquefied by free cold from the liquid nitrogen so that liquid natural gas (LNG) is produced. The LNG travels to an LNG destination tank for storage and/or transport. The liquid nitrogen is vaporized in the heat exchanger. The resulting nitrogen gas is directed to a process system that may include, for example, cylinders for welding or other applications. Between liquefaction cycles, the purifier is regenerated by a vacuum and nitrogen vapor from the head space of the source tank. Steel shot is mixed with absorbent in the purifier so that the absorbent is cooled for increased performance.

What is claimed is:  
     
       1. A system for liquefying a cryogenic gas using free cold from a cryogenic liquid, where the free cold would otherwise be wasted when the cryogenic liquid is vaporized, comprising: 
       a. an insulated source tank containing a supply of the cryogenic liquid;  
       b. a heat exchanger having a gas inlet, a liquid outlet, a liquid inlet and a gas outlet where the gas inlet is adapted to receive a feed of the cryogenic gas and the liquid inlet is in communication with the source tank;  
       c. means for transferring cryogenic liquid in circuit between said source tank and the liquid inlet of said heat exchanger;  
       d. an insulated destination tank in communication with the liquid outlet of said heat exchanger;  
       e. a process system in communication with the gas outlet of said heat exchanger, wherein the process system includes one or more cylinders; and  
       f. a vaporizer selectively in circuit between said source tank and said process system, said vaporizer selectively receiving cryogenic liquid from said source tank and vaporizing it so that a resulting gas flows to the process system,  
       whereby cryogenic liquid from said source tank flows to said heat exchanger when said means for transferring cryogenic liquid is activated and cryogenic gas from the feed flows to said heat exchanger so that the cryogenic liquid is vaporized in the heat exchanger by heat from the cryogenic gas and the cryogenic gas is liquified in the heat exchanger by the free cold from the cryogenic liquid and a resulting vaporized cryogen flows to the process system and a resulting liquefied cryogenic gas flows to the destination tank.  
     
     
       2. The system of  claim 1  wherein said means for transferring cryogenic liquid is a pump. 
     
     
       3. The system of  claim 1  further comprising a manifold in communication with the gas outlet of the heat exchanger so that multiple cylinders may be filled with gas from the heat exchanger. 
     
     
       4. The system of  claim 1  wherein the cryogenic gas is natural gas. 
     
     
       5. The system of  claim 4  wherein the cryogenic liquid is nitrogen. 
     
     
       6. The system of  claim 4  wherein the cryogenic liquid is argon. 
     
     
       7. The system of  claim 1  wherein said destination tank is mobile. 
     
     
       8. The system of  claim 1  wherein said destination tank is stationary. 
     
     
       9. The system of  claim 8  wherein said destination tank includes a dispensing line and a dispensing valve. 
     
     
       10. A method for liquefying a cryogenic gas with free cold from vaporizing a cryogenic liquid comprising the steps of: 
       a. providing a heat exchanger, a purifier having an absorbent wherein the purifier is adapted to receive the feed of cryogenic gas to be liquified, a destination tank and a process system;  
       b. purifying the cryogenic gas in the purifier;  
       c. directing the cryogenic gas to the heat exchanger;  
       d. transferring the cryogenic liquid to the heat exchanger;  
       e. warming the cryogenic liquid in the heat exchanger with heat from the cryogenic gas so that the cryogenic liquid is vaporized into a resulting gas and the cryogenic gas is liquefied with the free cold into a resulting liquid;  
       f. filling the destination tank with the resulting liquid; and  
       g. directing the resulting gas to the process system.  
     
     
       11. The method of  claim 10  wherein the process system includes one or more cylinders. 
     
     
       12. A system for liquefying a cryogenic gas using free cold from a cryogenic liquid, where the free cold would otherwise be wasted when the cryogenic liquid is vaporized, comprising: 
       a. an insulated source tank containing a supply of the cryogenic liquid;  
       b. a heat exchanger having a gas inlet, a liquid outlet, a liquid inlet and a gas outlet where the gas inlet is adapted to receive a feed of the cryogenic gas and the liquid inlet is in communication with the source tank;  
       c. means for transferring cryogenic liquid in circuit between said source tank and the liquid inlet of said heat exchanger;  
       d. an insulated destination tank in communication with the liquid outlet of said heat exchanger;  
       e. a process system in communication with the gas outlet of said heat exchanger; and  
       f. a purifier in communication with the gas inlet of the heat exchanger, said purifier containing an absorbent and adapted to receive the feed of the cryogenic gas that is to be liquefied;  
       whereby cryogenic liquid from said source tank flows to said heat exchanger when said means for transferring cryogenic liquid is activated and cryogenic gas from the feed flows to said heat exchanger so that the cryogenic liquid is vaporized in the heat exchanger by heat from the cryogenic gas and the cryogenic gas is liquified in the heat exchanger by the free cold from the cryogenic liquid and a resulting vaporized cryogen flows to the process system and a resulting liquefied cryogenic gas flows to the destination tank.  
     
     
       13. The system of  claim 12  further comprising a vacuum pump selectively in communication with the purifier, said vacuum pump pulling a vacuum on the purifier when activated. 
     
     
       14. The system of  claim 12  wherein said source tank includes a head space filled with a cryogenic vapor and further comprising: 
       g. a line running from the head space of the source tank to the purifier; and  
       h. a valve positioned in said line so that when said valve is open, cryogenic vapor from the head space of the source tank travels to said purifier so that the absorbent therein is flushed with the cryogenic vapor.  
     
     
       15. The system of  claim 14  wherein the absorbent of said purifier is mixed with shot constructed of a heat absorbing material that is cooled by the cryogenic vapor from the head space of the source tank. 
     
     
       16. The system of  claim 15  wherein said shot is made of steel. 
     
     
       17. A method for liquefying a cryogenic gas with free cold from vaporizing a cryogenic liquid comprising the steps of: 
       a. providing a heat exchanger, a purifier, a destination tank and a process system;  
       b. purifying the cryogenic gas in the purifier;  
       c. directing the cryogenic gas to the heat exchanger;  
       d. transferring the cryogenic liquid that is provided in a source tank with a head space containing cryogenic vapor to the heat exchanger;  
       e. warming the cryogenic liquid in the heat exchanger with heat from the cryogenic gas so that the cryogenic liquid is vaporized into a resulting gas and the cryogenic gas is liquefied with the free cold into a resulting liquid;  
       f. filling the destination tank with the resulting liquid;  
       g. directing the resulting gas to the process system; and  
       h. flushing the purifier with the cryogenic vapor from the head space of the source tank.  
     
     
       18. A method for liquefying a cryogenic gas with free cold from vaporizing a cryogenic liquid comprising the steps of: 
       a. providing a heat exchanger, a purifier, a destination tank and a process system;  
       b. purifying the cryogenic gas in the purifier;  
       c. directing the cryogenic gas to the heat exchanger;  
       d. transferring the cryogenic liquid to the heat exchanger;  
       e. warming the cryogenic liquid in the heat exchanger with heat from the cryogenic gas so that the cryogenic liquid is vaporized into a resulting gas and the cryogenic gas is liquefied with the free cold into a resulting liquid;  
       f. filling the destination tank with the resulting liquid;  
       g. directing the resulting gas to the process system; and  
       h. pulling a vacuum on the purifier.